Method parsePrefix

scripts/rubi/wl-parser.ts:279–325

()

  }

  private parsePrefix(): Json {
    const t = this.next();
    if (t.kind === 'pattern') {
      // `a_` → ["Blank","a"], `x_Symbol` → ["Blank","x","Symbol"],
      // `b_.` → ["BlankOptional","b"], `_` → ["Blank",""]
      const node: Json[] = [
        t.optional ? 'BlankOptional' : 'Blank',
        mapSymbol(t.name),
      ];
      if (t.head) node.push(t.head);
      return this.parsePostfix(node);
    }
    if (t.kind === 'punct') {
      if (t.value === '-') {
        const arg = this.parseExpression(PREC_UNARY_MINUS + 1);
        return negate(arg);
      }
      if (t.value === '+') return this.parseExpression(PREC_UNARY_MINUS + 1);
      if (t.value === '!') return ['Not', this.parseExpression(PREC_NOT + 1)];
      if (t.value === '(') {
        const e = this.parseExpression(0);
        this.expect(')');
        return this.parsePostfix(e);
      }
      if (t.value === '{') {
        const items: Json[] = [];
        if (!(this.peek()?.kind === 'punct' && this.peek()!.value === '}')) {
          items.push(this.parseExpression(0));
          while (this.peek()?.kind === 'punct' && this.peek()!.value === ',') {
            this.next();
            items.push(this.parseExpression(0));
          }
        }
        this.expect('}');
        return this.parsePostfix(['List', ...items]);
      }
      throw new Error(`unexpected token '${t.value}'`);
    }
    if (t.kind === 'number') {
      // strip precision marks like 1.5`20
      const v = t.value.split('`')[0];
      return this.parsePostfix(v.includes('.') ? parseFloat(v) : parseInt(v));
    }
    if (t.kind === 'string') return ['Str', t.value];
    // symbol — possibly a function call F[...]
    return this.parsePostfix(mapSymbol(t.value), t.value);
  }

  // Handles postfix forms after a head: calls F[a, b][c]…, Part
  // `lst[[1]]`, and derivative marks `F'[x]`.